A photomask used by photolithography and a process of producing the same

Claim 2

A photomask according to claim 1, comprising a first transparent layer pattern forming a first resist pattern, and a second transparent layer pattern formed reversely to the first transparent layer and forming a second resist pattern, the first and second resist pattern being identical in shape.

Claim 3

A photomask according to claim 1, wherein the transparent layer pattern (2) comprises a repetition of a line and space arrangement.

Claim 4

A photomask according to claim 3, wherein the pitch of the line and space arrangement is in the range of 1.0 µm to 3.0 µm.

Claim 5

A photomask according to claim 1, wherein the transparent layer pattern (2) comprises a matrix arrangement.

Claim 6

A photomask according to claim 5, wherein the pitch of the matrix arrangement is in the range of 1.0 µm to 4.0 µm.

Claim 7

A photomask according to claim 1, wherein the transparent layer contains a silicone-base resist pattern (7) formed on the transparent substrate (1), the resist pattern (7) containing siloxane polymer.

Claim 8

A photomask according to claim 1, further comprising a transparent electroconductive layer of ITO formed on the transparent substrate (1).

Claim 9

An exposure system comprising a photomask according to claim 1, wherein the transparent pattern (2) is repeated by a pitch below a resolution limit R represented by the following equation: R = k 1 * λ/NA where k 1 is a constant having a value of about 0.35, λ is a wavelength of incident light, and NA is the numerical aparture of an optical lens used in an optical projection system.

Claim 10

An exposure system comprising a photomask according to claim 9, wherein a distribution of the light intensity of the light passing through the photomask comprises a repetition of patterns having a pitch below the resolution limit.

Claim 11

An exposure system comprising a photomask according to claim 9, wherein the transparent pattern (2) is repeated by a pitch of not larger than four times the value of the resolution limit R.

Claim 12

An exposure system comprising a photomask according to claim 9, wherein the transparent layer pattern (2) is repeated at a pitch finer than the degree at which optical resolution is possible, so as to form a single resist pattern having a large area.

Claim 13

An exposure system comprising a photomask according to claim 9, wherein the pattern comprises a repetition of pattern having a pitch below a resolution limit which becomes a light-shielder against an irradiated light, and a transparent part of a repetition of pattern having a pitch above the resolution limit.

Claim 14

An exposure system comprising a photomask according to claim 9, wherein the transparent layer pattern (2) has equally spaced projections in opposite directions, the projections having a width 1 being less than the resolution limit R and projecting length m at both sides of the transparent layer pattern (2).

Claim 15

An exposure system comprising a photomask according to claim 14, wherein the transparent layer pattern (2) forms a line and space resist pattern having a line width virtually equal to 2n, the symbol n representing a half width of the sum of the width m and a width of the transparent layer pattern.

Claim 16

An exposure system comprising a photomask according to claim 9, wherein the transparent layer pattern (2) comprises an inner phase shifter (2a) and an outer phase shifter (2b) along both sides of the inner phase shifter (2a), where both a width n of the outer phase shifter and an interval m between the inner phase shifter (2a) and outer phase shifter (2b) are less than the resolution limit R.

Claim 17

An exposure system comprising a photomask according to claim 16, wherein the transparent layer pattern (2) forms a line and space resist pattern where the line width is virtually equal to 2ℓ, the symbol ℓ being a distance between the centers of the inner phase shifter (2a) and the outer phase shifter (2b).

Claim 18

A process for forming a photomask comprising the steps of: coating the transparent substrate (1) with a transparent layer (9) or depositing a transparent layer (9) on the transparent substrate (1) to sufficient thickness; and exposing predetermined portions of the transparent layer (9) to light or electron radiation so as to form a transparent layer pattern (2), to give a phase difference between light passing through the transparent layer pattern (2) and light passing through the substrate (1) of 180° multiplied by an odd number; wherein the amount of the exposure is varied so as to form a part of the periphery of the transparent layer pattern (2) slanting in cross-section, the slanting part thinning continuously.

Claim 19

A process according to claim 18, further comprising the step of forming a transparent conductive layer on the transparent substrate (1).

Claim 20

A process according to claim 18, wherein the transparent layer (9) is coated with a resist, the resist pattern (7) is formed by the exposure, and the predetermined portions of the transparent layer (9) are removed by the use of the resist pattern (7) as a mask, so as to form the transparent layer pattern (2).

Claim 21

A process according to claim 18, wherein the transparent layer pattern (2) is formed by removing the resist pattern (7) so as to enable a transparent pattern to remain on the substrate (1).

Claim 22

A process according to claim 20, wherein the resist is exposed by changing the amount of exposure.

Claim 23

A process according to claim 18, further comprising the steps of coating the transparent layer (9) with a resist, and effecting the exposure of a part of the periphery of the resist by light whose focus is deviated.